1. Field of the Invention
The present invention relates to a technique to estimate powers which are enabled to be inputted to a secondary cell and which are enabled to be outputted from the same secondary cell.
2. Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 9-171063 published on Jun. 30, 1997 exemplifies a previously proposed battery power calculating apparatus. In the previously proposed battery power calculating apparatus described in the above-identified Japanese Patent Application First Publication, an equation (V=R×I+Vo) expressing an I-V straight line characteristic representing a discharge characteristic of the cell is calculated on the basis of a current I and a terminal voltage V supplied from a cell, an internal resistance R of the cell is calculated from its gradient, and an electromotive force Vo (which corresponds to a terminal voltage during a current interruption and also called an open voltage or open-circuit voltage) of the cell is calculated from an intercept. A minimum guarantee voltage value Vmin to guarantee a cell life on the basis of current I and cell temperature T is calculated and is substituted into the equation of I-V straight line to determine a maximum current value Imax. The output enabling power value P is calculated from an equation of P=Vmin×Imax.